Spring and method of making the same



May 13, 1941. I A. J-. BERG EI'AL i 2,241,388

sink-me AND METHiQD OFMAKING Tm: smi

Original Filed Dec. 8, 1937 I 10. 1/ Ila l2 5 1 INVENTORS ALFRED J- BERG JOHN 0. 1 H055 ATTORN Patented May 13, 1941 Alfred J. Berg, Portsmouth, N. H., and John 0. Huse, United States Navy Original application December 8, 1937, Serial No.

178,698. Divided and this application Decemher 15, 1939, Serial No. 309,420

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 2 Claims.

Our invention relates primarily to a new and useful method of and tool for making a spring.

This invention is an improvement upon our invention disclosed in an application for Letters Patent entitled Spring and method of making the same, Serial No. 178,698 and filed December 8, 1937, and to which reference may be had for a fuller understanding of the present invention and the problems overcome thereby.

Instead of making springs from the more expensive vforms of metal, which are rolled or drawn to the shape in cross section desired for the spring, we shear-cut the spring of its desired shape and cross section from a larger piece which is a comparatively inexpensive form of the metal.

We have found that our present invention produces a very useful, durable and efficient spring at a substantially lesser cost than has been heretofore possible with the employment of the prior practice of making springs.

While springs of many kinds may be advantageously made byour invention, the same is very advantageously employable in'the making of the usually more expensive form of spring known as the helically coiled spring.

According to our invention embodied in the beforestated application, the spring is cut from larger mletal by a cutter having a substantially straight cutting edge, which, with other characteristics of said cutter, cold works the metal of the severed spring to render the metal of the severed spring more advantageous for spring purposes. According to our present invention we likewise sever the spring metal by a cutter having a cutting edge which shears the metal. In the present invention the cutting edge of the cutter is not in a straight line when viewed from one side of the cutter. but varies in hei ht at different points in the length of the cutter. This cutting edge not only compresses the metal in advance of the cut but causes some flow of the metal being cut alongthe edge of the cutter, while other characteristics of the cutter afford to the cut spring additional cold working which we have found advantageous in springs.

Other features, objects and advantages of our invention will be rendered apparent from an understanding of the following specification and the drawing.

In the drawing, in which like characters of reterence indicate the same parts,

Fig. l is a top plan view of a portion of a lathe, or other turning tool, in the act of turning a helical spring having a central hole therethrough from the end of a tubular bar of metal with an independent stationary bar entering the hole in the bar to receive thereabout and support the spring as severed;

Fig. 2 is a plan view similar to Fig. 1, but showing the spring being turned from the end of a solid bar of metal, with the severed spring as the only shaving resulting from the operation, and leaving a central projection integral with the end of said bar for supporting the severed portion of the spring by its periphery engaging the central hole through the severed portion, all performed ata single operation;

Fig. 3 is a side elevation view of the cutting portion of a turning tool employed in the instance shown in Fig. 1;

Fig. 4 is a front-or outer end elevation view of the turning tool shown in Figs. 1 and 3;

Fig. 5 is a side elevation view of the outer porticn of the turning tool shown in Fig. 2;

Fig. 6 is an elevation view of the outer-end of the turning tool shown in Figs. 2 and 5;

Fig. '7 is a side elevation view of a modified form of the turning tool shown in Figs. 2 and 5;

Fig. 8 is an end elevation viewed from the outer end of the turning tool shown in Figs. 2 and 7,

Figs. 9 and 10 are top plan views of modified forms of the outer portion of the turning tool shown in Figs. 2 and 5;

Fig. 11 is a side elevation view of a portion 01' a'helical spring made and characterized according to our invention; and t 7 Figs. 12, 13 and 14 are enlarged cross sectional views of modified forms of the metal comprising the spring helices.

The revolvable spindle l2 of the usual or any conventional type of lathe, screw machine or other turning tool, may be fitted with chuck I0 provided with adjustable holding jaws I 0a, or other suitable means, for securing thereto one end of a tubular bar of metal I I. in whose longitudinal opening extends a preferably rigid bar llb, Figs. 1 and 3, having a notch llbb in one side thereof. The shank l5 of a turning tool having a cutting edge I! longitudinally disposed along the outer end thereof is suitably mounted in a conventional tool post I3 secured upon a carriage 13a with said edge I! extending parallel with and. in close proximity to an end of said bar H, with. the outer end of the turning tool provided ith the cutting edge I! extending from beyond the-outer periphery to the cenral opening in bar H, and may extend into said notch llbb to insure the complete severance of the whole width of the spring from the end of bar II. A turning tool I4 of usual construction is mounted in tool post I3 at the side of the turning tool I5 for turning true the outer surface of the bar II in advance of the severance of the spring I la therefrom by the cutting edge H of the turning tool I5.

In Fig. 2 the bar Hub of metal, from the end of which the spring I Ia may be helically turned, is solid, and the outer end of the cutting edge I1 is so constructed as to sever the spring from the end of the bar at a point sufliciently removed from they longitudinal axis of the bar IIab to form the central longitudinal hole through the spring Na, and at the same time to form in the center of the end of the bar II ab a projection I Id integral with the bar I Iab and of a diameter coincident with that of the central opening through the spring Ila. This projection IId enables cheaper metal in the form of a solid bar [lab to be used as the parent stock from the end of which the helical spring of our invention may be turned rapidly, economically and efficiently, instead of employing the more expensive metal in the form of tubular bar'li shown in Fig. 1.

s In each of Figs. 1 and 2 the tool post I3 rigidly mounted uponthe carriage I3a, is moved longitudinally at a definite, desirable, predetermined rate proportionate to the revolvable movement of thebar II or I Iab, the relative rate of such 1ongitudinal movement determining the thickness of the metal comprising the spring helices.

In each of Figs. 1 and 2 the spring Ila is the only shaving resulting from the operation of our invention, except where turning tool I4 is employed to true up the outer diameter of the bar II or Nob. Thus, in accordance with our invention, practically no waste of metal occurs, as even the projections Ild, remaining after the solid bar Ilab has'been turned completely into springs IId, may be used as true turned stock which commands 'a highprice in the metal mar ket.

There. are"substantial differences in structure and characteristics between the turning tool I2 of ourafores'aid'application and the turning tool I5 of the present application, as well as between the like tools illustrated in Figs. 1 and 2.

Relative to our aforesaidapplication, the shavings of the prior'art were wholly or mainly waste product, whose length was required to be 'broken up ;into relatively short piecesto preclude the possibility of personarinjury to the operators of the machines, as w-ell' as damage to property. By our inventions the turned helical spring is the shaving comprising'the useful spring, which is afforded desirable spring characteristics'by the cold working of its constituent meta-l by'the characteristics of theturning tool I2. The characteristics of the turningtoo1I'5 of our present invention afford acold working to the constituent metal of thespring -I Iw when severedfrom its parent bar II or IIa-b, quite differently, by substantially different characteristics of said turning tool I5, to providenstill different valuable pr-operties for. sprin purposes 'to' the severed spring I la.- One. ofthese characteristics of our present invention is that the cutting edge H of the turn-' ing tool I5 .does' not extend in a straightline nor radially from the point of the neutral axis of the bar II or Ijab, or. radially from a pointapproximately one thirty-second of an inch above or below.such neutral axis, pursuant .to the turning practice taught by the prior art for many years asessential to good turning; but theedge Ii varies in height at different points in the length of the turning tool. In the meanderings of cutting edge i'I to differentheights at varying points in the length of the turning tool I5, such edge violates the teachings of the prior art by substantially departnig from the requirement of the prior art for good turning that the cutting edge should be upon a line exending radially from the neutral axis of the bar from an end of which the shaving was to be cut, or extending radially from a point about one thirty-second of an inch above or below such neutral axis. In the instance shown in Fig. 3 the cutting edge H extends from within the recess IIbb of the stationary bar lib to a point beyond the outer diameter of the bar ll. The metal of bar II at its central opening is engaged by the cutting edge ll of the turning tool I5 at a point subtsantially below a horizontal plane passed through the neutrol axis of the bar II, Fig. 3, and extends upwardly and outwardly across the end of bar II in a curved path in the instance shown. This curved" path in such instance has its highest point substantially above -said plane, and the metal of the outer edge of bar II is adapted to engage said edge IT at a point above said plane and preferably below the highest point of said edge; In said instance, said edge II throughout its engagement with the metal of the end of bar I I, extends above a plane passed through the point of its engagement with the meta-l of bar II at its adjacent inner and outer edges, and which plane passes at a downward angle below the neutral axis of the bar I I. The metal of the turning tool I5, Whose upper surface bears said edge I'I, may be somewhat thinner than the body of the shank of said tool I5. Its lateral or side rake surface I'Ia', which extends downward at an angle from the edge I1, is beveled, and preferably slightly arched vertically and longitudinally as it extends from edgel'l'downwardly and outwardlyto the lower edge of the turning tool I5. The severed portion of spring Ila passes over and in firm contact with said surface lid. -The lateral clearance surface of the tool I5 is slightly beveled downwardly and away from said edge I'I, commencing at a point below the hereinafter stated nicks ll, so asto avoidlfrictional contact of said surface with the end of bar II at any point in the extent of said bevel -While said edge I? is sharp, it is supported by metal of tool l5 of substantial and progressively increasing thickness from said edge II to the bottomof tool I 5. Consequently, incutting thespring Ila the density of the metal of bar II immediately in advance of said edge I'I, while such cutting is progressing, is increased in density by the force required for said cutting. This not only cold works at least a portion of the metal of the spring I ia being thus severed, but it likewise cold Works the metal of the adjacent surface of the bar II which will comprise the portion of spring IIa to be subsequently cut from bar II, 'in the instance that the spring [la is a helical spring, or the surface of the succeeding spring Where a fiat or non-helical spring is" to be cutac'cording to our invention. It will be understood'that the terms cold worked or cold working, when employed herein, refer to the metal being out being at substantially room or atmospheric temperature andsubstantially unheated, except that arising from the force and friction of cutting, which heat, in some respects, is appreciably and 'designedly increased by our invention. i

The metal of the portion' of spring Ila being severed by said cutting edge II, being-rendered of increased density at and above said cutting edge H, as :aforesaidis passedat 'a sharp outward angle from the end of bar H by, rover sand downwardly across the surface i-l'a of the turning tool l5. This still further .cold Works the metal of the severed portion of the spring by increasing the density of the'metal of-thexouter surface of the severed portion of the-spring, and by slightly reducing the density, or stretching, the metal of the opposite surface of the severed portion of the spring which is in contact with said surface l'la of the turning or cutting tool I 5. This last stated further cold working of the spring simultaneously with its severance from the bar ll even'visually'transformsthe-appearance of the surface of the metal of the severed spring visible to the unaided eye, especially where the severed spring is of copper. zSuch transformation is most evident upon that surface of the severed portion of the spring which does not come in contact with the surface lid of the turning tool or cutter [5. While the freshly cut or end surface of bar I I, which comprises the surface of the spring in question when the same is severed, is bright, the same is transformed at a point opposite the cutting edge I! into a dull or frosted appearance progressively as the metal is being severed and commences to pass at a Wide angle onto and over the surface lie of the turning tool or cutter I5. This seems clearly to be due to the compression or further compression of the metal of such surface of the spring as the same is being severed. Simultaneously with such compression, the metal of the opposite surface of the spring being severed, at least a part of which was compressed and its density increased by the force incident to severing the spring from the bar I l, is somewhat stretched and polished as the beveled portion of the spring passes outwardly at a sharp angle from bar H and upon and over the surface !!a of the turning tool or cutter l5.

The cutting edge H of turning tool or cutter [5 being not in a straight line as viewed in side elevation, but of varying height at different points in its length, gives to the spring severed thereby from larger metal characteristics which we have found advantageous for spring purposes. Such characteristics, in addition to those heretofore indicated, typically are (a) that in the prior art turning practice where a metal shaving may be helically cut from an end of a bar, by a tool or cutter whose straight cutting edge usually extends radially from the neutral axis of such bar and the shaving breaks into short pieces, due to such radial cut and its action upon the metal of the bar which, in some metals, has a grain which is cross-cut at some points, and cut with the grain at other points about the circle of said bar. 7 Where the grain is cross-cut by the process of the prior art, the shaving is broken by the process of cutting into small bits. However, by our invention even metal having a grain which may be cross-cut produces shavings which may be used as springs of substantial length, due to the before stated, as well as the hereinafter stated, characteristics which our invention affords to the severed prin (b), that the metal being severed by said edge I! under the before stated substantial pressure of the cutting which results in the increased density of the metal about the cutting edge, also causes some flowage of particles of the metal longitudinally along said edge I! from a higher to a lower :point along said edge 1| 1.; (c) said edge 1.! simultaneously and progressively cuts as well asstretches the metal of, andiin the direction of the width of, the spring, or each helices thereof. The highest point of the cutting edge I! seversta portion of the width of the spring, or sprin helices, while portions of the bar H on opposite sides of such high point are still integral with and unsevered from the "bar H. Such partial severance necessarily results in a progressive stretching of the metal, due to the substantial angle, as well as outwardlateral and longitudinal curvature of the surface Ha of the turningv or cutting tool l5. Such surface Ha being associated with the high as well as other points in thelengt-h of thecutting edge ll, and the fact thatportions of the metal of bar II on opposite sides of the high point in cutting edge I! are sti-ll'unsevered from the bar ll, the intermediate severed portion of the spring Ila is substantially stretched by and to the extent 'of the penetration of the surface Ha of tool 15 into the metal of the end of bar H before the edge 11 breaks through the inner and outer surfaces of theend of bar H being cut. The magnitude of such stretching may be determined Figs. 3 and. 7 "by placing a straight edge across the points in cutting edge l1 contacted by the inner and the outer diameters of the bar H or the inner and outer edges of the spring or spring helices in the instance shown in Figs. 2 and '7,

and by the thinness-of the cutting edge I. compared to the-varying thickness of the tool in its extent between the points Where-the inner and outer edges of the severed spring contact the cutting edge II. This progressive stretching the metal in the direction of the width of the spring occurs simultaneously and progressively with the aforesaid increasing density or compression stress'u'pon the metal inthe region at and slightly above the cutting edge II, which latter tends to compress and'stress the metal of the spring in along-itudinal direction; (03) additional cold working of the metal of the severed portion of the spring, as well as additional strength to the severed spring itself, we have attained by placing one or more nicksZl in the cutting edge .17, as indicated in Figs. 7 through 10. Each nick 2| is associated with a groove 22 registering with-each nick at one end and extending over the surface Ha of the tool l5. In the instance shown each of these grooves Here in the arc of a circle whose center iscoincident with the neutral axis of the bar H or I lab. Such nick or nicks 21 may be placed in the edge H of any form of the cutting edge of the tool 15. The nick or nicks 2i form no break in the vertical cutting face of-the tool l5 at whose upper margin is the cutting edge l1, and consequently form noridge upon the end of the bar H or Hub, from the end of which the spring maybe severed. In severing the spring with the cutter provided with the nick =or nicks 2! and grooves 22 its cutting action is as heretofore described, together with that resulting from the nicks and grooves. In such cutting the edge i1 severs the metal in advance of the severance thereof by the bottoms of the nicks 21. This results in the metal severed by the edge i? being started to flow therefrom into and over the initial portion of the surface Ha, while the portion of cutting edge I! forming the edge :of the nicks '2l is receiving the metal and commencing to cut the same from the bar 'H or 1 lab. 'Astne metal within the groove or grooves 22 is severed it started to extend along such groove or grooves, in which the metal initially filling the initial edge of each groove 22 proceeds to extend along each such groove 22 and to stretch the metal lying in each such groove 22. This pressure of the cutting and sliding of the metal in and along each groove results in the formation along the length of the spring Ila of a corrugation 23 for each nick 2| and groove 22 in the tool I5. The convex side of the corrugation 23 conforms to the shape of the groove 22, while the opposite concave portion thereof is not defined by direct contact with any part of the tool I5 but results merely from the stretching of the metal of the spring Ila by the force of cutting the metal included within each groove 22 by the cutting edge I'I, which forms each nick 2!, and which results in the formation of the convex side of grooves 22 and corrugation 23 in spring Ila.

Each of the before mentioned forms of cold working the metal transforms the characteristics of the metal of the severed spring Ila from the metal of the bar II or IIab from which the spring is cut. Each of these transformation is produced simultaneously with the cutting of the spring, and extend continuously throughout the length of the severed spring, and afford to the metal of the severed spring characteristics which we have found very advantageous for spring purposes. One or more of these characteristics may be imparted to the spring according to the character and requirements of such service; while all of such characteristics enable the spring to function satisfactorily under severe service conditions.

In connection with Figs. 1 and 3, wherein the spring Ila is severed from the end of tubular bar II and the outer or tip end of the turnin tool or cutter l5 which extends within the bore of tubular bar II and into the notch Ilbb of rigid bar IIb, whose end extends within the bore of said bar II while the periphery of bar I Ib receives and supports from lateral vibration the helical coils of spring Ila as severed from the end of bar II, such outer or tip end of the tool I5 performs no function. However, to equip the tool l5 of Figs. 3 and 4 for dispensing with said bar IIb bycutting the same from the end of the solid bar Ilab, Fig. 2, and leaving a central integral projection (Z of bar Ilab to support from lateral vibration'the spring IIa as severed progressively from the end of bar IIab, such outer or tip end is provided with a terminal surface l'lh. extending downwardly from the outer end of cutting edge 11, which edge I! is joined at its outer end by a cutting edge IIj which forms the outer margin of the beveled surface I'Ia of said tool I5. Below said surface Hit, the tool I5 is provided with an outer surface I'Ii which extends to the bottom edge of the tool I5 and supports the metal of the outer end of tool I5 having the surface Hit, the downwardly and-laterally extending cutting edge I1? and the outer end of the cutting edge I'I.

To helically turn or cut a helical spring Ila from the end of solid bar II ab, Fig. 2, the point or outer cutting end of the tool I5, represented by the juncture of the cutting edges I! and I17, is adjusted across the outer end of bar II ab until said juncture is brought to the point within the circumference of bar llab to define the diameter of said projection Ild of bar Ilab, as well as the edge of the central opening through the spring to be severed. Whereupon, the bar II ab and said tool I5 are relatively rotated and longitudinally moved. Thereupon the cutting edge I! of tool I5 commences to cut the lateral surface of spring Ila from the end of solid bar Ila-b, and simultaneously therewith the cutting edge I'Ij commences to cut the inner edge of the spring Ila from the bar Ilab, which simultaneously forms the central opening through the spring and the integral projection (Z of bar Ila which occupies such central opening, and precludes the lateral vibration of the severed portion of the spring which would otherwise result from the rapid rotation and helical cutting. The cutting edge I11 directly joining with the outer end of the longitudinal cutting edge I! of the tool I5 results in the formation of a square or right angled edge Me of spring Ila, Fig. 13.

We have further found that said cutting edge I'Iy' of tool I5 may be dispensed with by providing the outer end of the tool I 5 with a curve I'In, Figs. 5, 6 and 9, which joints with and extends laterally from the outer end of cutting edge IT. The lateral extent of said curve I'In exceeds the thickness of the metal of the spring Ila to be severed from thicker metal, and the outer edge of the curve I'In is a cutting edge. In the tip or outer end of tool I5 comprising said curved cutting edge I'In is a nick I'Im. In the employment of the tool I5, shown in Figs. 5 and 9, an initial cut is made upon the outer end of bar lIab by the tool having the joined cutting edges II, IIn, in which the curved cutting edge IIn forms upon the end of bar Hal) a flat annular surface represented by the edge I'l' having at its inner margin a curve IIn, Fig. 14. In the cutting of the spring Ila from such bar the inner edge of the spring, which forms the central opening through the helically cut spring, is formed by two like curved surfaces lln, Fig. 14, whose somewhat parallel surfaces are spaced apart conformable to the thickness desired of the metal of the spring. At the inner edge of the helical spring Ila, which forms the central opening through the spring, the curves lln merge into each other, and this point of merger defines the periphery of the integral projection lid of the bar IIab as well as the opening through the spring, and also forms the lateral projection Ilc of spring Ila. This curved cutting edge I'In and nick I'Im also cold work the metal of the edge of the spring forming the projection Ho and between the curves Iln. In such cold working the nick Ilm greatly increases the top rake or bluntness of the beveled surface IIa of tool I5. This increased bluntness greatly increases in the region of said nick Ilm the density of the metal at and in advance of being out by the cutting edges I'I, lln, which border the nick Ilm, due to the substantial increase of the force required to sever the metal in the region of nick I'Im, due to the increased bluntness of the surface Ila afforded by the nick I'Im. Said cold working also produces in the severed spring characteristics which we have found to be advantageous for spring purposes.

In Fig. 10 is shown a modified form of the cutter shown in Figs. 5 and 9, in which the curved cutting edge Mn is dispensed with and a short cutting edge Hg) is substituted therefor which at one end joins at a right angle the outer end of cutting edge II, and its remaining end extends to the width of the nick I'Im which exceeds the width of the spring to be cut and produces a square or right angled edge of the spring,

senses asshownat He in Fig. 13. Simultaneously with the formation or this inner edge II'e of spring I Ia my said cutting edge I11) and its accompanying nick I 1m, Fig. 10, the metal comprising such-edge is cold worked substantially the same described in connect'ion-with Figs. 5, 6, and 9. In Fig. 3 the cutting edge 11 of tool I 5 clips "or meanders mainly downward toward the central portion of the bar II, which causes 'a nowage 'of metal along cutting edge I! mainly toward thece'nter of bar II. However, in Figs. 7 and 8 is illustra'te'd a tool I5 whose cutting edge I! is highest at a point at 'or near the center of the width of thespring to be out. From this high point the cutting edge I! dips or meanders in 'oppositedirec'tions toward the opposite edges of the's'pring to be cut. In this case, the flowage ofsome of the metal being cut occurs along the edge I I in opposite directionson opposite sides of the high point of the cutting edge II, which is'toward opposite edges of the spring being cut.

'formed with their registering nicks 2i in the cutting edge Ii.

While in our before-mentioned application, the grooves 22 are not disclosed as concentric with the neutral axis of the barII or IIab, such grooves 22 are herein shown to be curved, and which curves may be or approximate to concentric with such neutral axis.

Cutting tools cutting in a continuous straight line, where, for instance, the cutting tools are mounted in a machine tool known as a shaper or a planer, and which cutting tools have the characteristics, or any of them, of the herein disclosed cutting tool I5, will cut a straight spring of our invention from a larger piece of metal and simultaneously cold work the same to thereby afford characteristics in the metal of the spring which we have found very advantageous for spring purposes.

It will be understood from the foregoing, by those skilled in this art, what comprises our method, and the transformed characteristics of the metal} of the severed spring. It will likewise be understood herefrom that the cutting edge I3 of tool I2 of our before-stated application does not make a shear cut, and that the cutting edges I1 and I'in of our present application do make. a shear cut; that the cutting edges I! of tool I5 of the present application may fairly be said to meander throughout the width of the spring to be cut and that its line of cleavage in the metal being severed may likewise be characterized; that the cutting edge I1 is adapted to meander somewhat radially into the end of the metal bar and to cut and simultaneously cold work progressively the lateral surfaces of the spring, while the cutting edge of tool I4, as well as the cutting edge Hit of Figs. 5, 6 and 9, the cutting edge I77 of Figs. 3, 4, '7 and 8, and the cutting edge lip of Fig. 10, each may fairly be said to extend longitudinally of the bar, said edge of cutter I 4 functioning to machine and define the outer edge of the spring whensevered, and .the 'remarning designated 'cutting edgesiunctioning to machine and define the inner edge of the spring as severed; while Fig. 1, and in dotted lines in Fig. 3, wherein the spring isturnedirom the end of .axhollow or tubular bar, the bore of the'tube defines the inner edge of the spring when severed; land that the cold workingof the metal occasioned by the cutting of the spring beneficially affects the metal of the spring which is being severed, as "well as the surface of the metal of the end of the bar from which the spring is being severed,

.and that in making a helical out, after making the first substantially full helices, which may be removed in cases :where not adapted .for 'the :service requirements of a particular spring, both lateral surfaces of the spring helices are equally cold worked *by the act of cutting the spring in addition .to the other species of cold workin heretofore described.

We have furthermore. observed that a helical spring made with a cutterdis'closed in Figs. 3 to 6, inclusive, by cutting from the end of a tubular bar the inner and outer diameters of the helical spring, will be less than the outer and inner diameters of thetubular bar from which the same is being cut, dueto the major slope of the cutting edge I! of "the cutting tool being toward the center of the bar I I; and that'when such major slope is toward the outer edge of the tubular bar, the inner and-the outer diameters of the severed spring are somewhat larger than those of the bar from 'which'the spring is being severed; and that in each case'o'f inequality in the diameters of the severed spring and the bar from which the'spring was severed, the edges of the severed spring and of the'bar from which it is cut coincide only progressively around the end of the bar as the spring is being severed. In the case of the spring being cut smaller than the diameter of the bar from the end of which the same was cut, the diameter of the stationary spring supporting bar I Ib is correspondinglydecreased.

The angles formed by the various faces of the tool I5 relative to its cutting edge H are considered as the surface Ila being the side rake, and the one extending at a slight angle below the edge I1 is the clearance. In the cutter of Figs. 3, 4, 7, :and 8, the cutting edge I17 forms the outer edge of the side rake, while the surface I 1h, Fig. 4, extending downward and slightly inward from edge I17 is the clearance. In the cutter of Figs. 5, 6, 9, and 10, the cutting edges IIn and lip are each provided respectively with clearances which are, as will be understood by those skilled in the art herefrom, contlnuations of the clearance of the edge I1. The neck I'Im, in the instances shown in Figs. 5, 6, 9, and 10, initially increases. the top rake normally aiforded by the surface Ila.

It will be understood that in the instances shown in Figs. 2 and 3 the cutting angle of the tool II, as well as its side rake angle represented by its surface I ia, are each normal for the material to be cut by the tool, but that the cutting edge or edges are provided with means I2b, 2| and 22, for increasing the effect of the top as well as side rakes of the cutter upon the material being cut by the tool. Such effect is to increase the cutting thrust of the cutter upon the metal being out, which cold works the metal being cut into an increased strength and toughness and as hereinbefore described.

Before our invention it was unknown that solely by cutting or turning a metal article, or a shaving therefrom, that such article or shaving .form of the required spring, which cold working transformed the characteristics of such metal into those which we have found beneficial and advantageous for spring purposes.

We are aware of aprior practice, termed Auto frettage, wherein high pressure liquid is directly applied within an ordnance bore to outwardly stress and stretch the metal of the wall of such bore beyond its elastic limit, but below its fracture point, to thereby transform the characteristics of imparting thereto increased In such practice, no

such metal by strength and toughness.

cleavage of metal is involved, and every precau- 'tion is exercised to avoid any fracture or cleavage of metal therein, as the same destroys the utility of the manufactured bore which is subsequently subjected to such practice. 3

In our invention, cleavage controlled to a'line conforming to a cut or turned surface of the metal of a required spring is a very desirable part of our invention. Such cleavage is occasioned by stressing the metal along such line of cleavage at least to its shearing point, while atleast the metal adjacent such line is subjected to compression stress beyond its elastic limit, but below its frac-' T ture point, which stress occasions a flowage of metal at least adjacent such line, although such metal may be at room temperature but for said stress. We have found that such stress may be associated with and occasioned by an abnormal .cleavage of the spring from a larger piece of metal, whose normal characteristics are unadapted for spring purposes, and that such cleavage beneficially transforms the characteristics of the metal so stressed and cleaved into a spring and into characteristics which we have found "advantageous for spring purposes. While said stressing of the metal involves the application of force in excess of that required for the normal cutting or turning of a like extent of similar metal, the magnitude of such stress required to cut or turn a spring is very materially reduced by the stressing being progressively and successively applied to different relatively small areas which may extend throughout a surface or surfaces of the met-a1 being cleaved into a spring. Such reduction in the magnitude of such stress also reduces the magnitude of the power required in the practice of our invention, as well as reduces the wear upon the machine and cutting tools which may be required for the practice of our invention;

While we have illustrated several forms of cutting or turning tools for the different cutting edges and other features, all of such features may be associated, when desired, with and in the cutting edges of a single tool.

This is a divisional application of our copending application Serial No. 178,699 filed December 8, 1937. n

. The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

We claim:

1. A cut spring comprising an integral metallic member having a flange extending along an edge thereof, the entire lateral surfaces of said member being formed by a cutting operation and cold Worked by the cutting.

2. A cut spring comprising a helical integra metallic member having a flange extending along one edge thereof, the entire lateral surfaces of said member being formed by a cutting operation and cold worked by the cutting.

ALFRED J. BERG. JOHN O. HUSE. 

